From one of the only two states in the union to legalize recreational marijuana use, new research is suggesting females, thanks to estrogen, are more susceptible than males to the drug's effects on the brain.

According to the findings out of Washington State University, recently published in the journal Drug and Alcohol Dependence and based on experiments with lab rats, females are at least 30 percent more sensitive than males to the pain-relieving qualities of Tetrahydrocannabinol, or THC, the principal psychoactive constituent of the cannabis plant, which is the primary active ingredient in cannabis.

It was further discovered females seem to develop a tolerance to THC more quickly than guys, study lead Rebecca Craft, a psychology professor at the university, said in a news release.

However, such heightened sensitivity may also increase vulnerability to pot's more negative side effects, such as addiction, as well as feelings of anxiety and paranoia.

Craft explained other researchers, including Margaret Haney at the Columbia University Medical Center, previously demonstrated women tended to be more affected through cannabis abuse and dependence than men.

Haney documented a cannabis withdrawal syndrome of irritability, sleep disruption and decreased food intake that appeared more severe in women.

Women, it was also found, had a greater risk of relapse as they tried to stop using the drug.

With legalization of recreational pot use in Washington and Colorado, and medical use allowed in many more states, Craft noted, it's vital researchers better understand the varying effects of cannabis on males and females.

"Marijuana is very different than it was 40 years ago," she said. "It's much higher in THC and lower in cannabidiol," one of the 60 or compounds that's been identified in cannabis and which is strongly linked to the drug's medicinal qualities.

"We're more likely to see negative side effects today like anxiety, confusion, panic attacks, hallucinations or extreme paranoia," she said. "And women are at higher risk."

Craft said she and her team "routinely manipulate hormones and follow females across their cycles to see if their drug sensitivities change along with their hormones. And they do ... very frequently, with estrogen being the culprit.

"What we're finding with THC is that you get a very clear spike in drug sensitivity right when the females are ovulating -- right when their estrogen levels have peaked and are coming down," she said. "A little bit goes a very long way."